1. Field of the invention
The present invention relates to an aeroponic apparatus, that is, to an apparatus adapted for soilless agriculture where the roots of plants are suspended in the air and are sprayed or misted with a nutrient solution. The spraying of solution in the air, combined with plant transpiration, serves to increase ambient humidity, particularly in dry environments as during dry seasons.
2. Description of the prior art
The growth of plants by aeroponic technique is not new. Thus, the subject has been treated in the following publications.
In an article by F. MASSANTINI in Soilless Culture (1985) pp. 85-96, entitled: "The light and dark sides of aeroponics";
In an article by B. VESTERGAARD in Proceedings of the International Society on Soilless Culture, (1984), pp. 723-738, entitled "Oxygen supply to the roots in different hydroponic systems", and
In a book entitled "Hydroponic Food Production" (1981), Woodbrige Press, Santa Barbara, California, 335 p.
The patent literature is also replete with patents on various apparatuses and methods for hydroponic or aeroponic plant production.
Of particular interest, with respect to the present invention, is U.S. Pat. No. 4,059,922, issued on Nov. 29, 1977, which discloses a hydroponic grower wherein potted plants are held in two inclined wall panels of an A-frame. This grower uses a single spray jet which is located at the bottom of a tank containing a nutrient solution. As the roots of the plants grow and develop, they create flossy curtains which hinder the passage of water spray and prevent it from reaching the smaller root structures of more recently potted plants. The use of a single spray jet further restricts the available height and the usefulness of the A-frame. Also, the high pressure necessary for the solution spray to reach the upper root structures, after having penetrated the aforesaid root curtains, is physically detrimental to the root structures of the plants located at a lower level, that is closer to the outlet of the spray head.
Additionally, the A-frame of U.S. Pat. No. 4,059,922 has the bottom edges of the confining walls sit directly at the bottom of the tank of nutrient solution of which the border thus becomes exposed to direct light and rapidly gives rise to algal growth. These algae are green to black, in color, and particularly unsightly. Furthermore, they feed on the nutrient solution and therefore the latter has to be changed frequently. With respect to exposition to direct light, it may be noted that a large aperture has to be provided through one of the A-frame walls, presumably to give access to the pump. This aperture allows light directly on the mass of nutrient solution, causing algal growth directly on the plant roots thereby reducing plant growth.
The A-frame, in this patent, is made of two parts which sit one over the other with no special means being provided to ensure tightness tending to prevent leakage of nutrient solution along the joints and consequently rapid formation of unsightly algae as well as salt deposit. Lack of such fastening provision further structurally weakens the A-frame. In this regard, there is also no mention of any structural support providing stability in windy environment and failing to take into consideration the increase in weight of the apparatus as the plants grow.
The watering system, in this U.S. patent, does not appear to be provided with any protection against clogging by peat, salt, dirt or organic accumulation which can rapidly clog it. Failure of the watering system of course causes rapid loss of the plants unless excessively frequent maintenance is implemented.
Additional examples of prior art devices for aeroponics or hydroponics are to be found in the following U.S. patents:
119,242 - 800,306 - 1,181,145 1,245,441 - 1,915,884 - 2,062,755 2,121,461 - 2,150,257 - 2,152,254 2,198,150 - 2,244,686 - 2,296,860 2,306,027 - 2,411,681 - 2,431,890 2,592,476 - 2,777,253 - 2,854,762 2,855,725 - 2,928,211 - 2,952,096 2,963,819 - 3,095,670 - 3,123,304 3,305,968 - 3,323,253 - 3,352,057 3,424,231 - 3,478,817 - 3,532,437 3,578,245 - 3,667,157 - 3,768,201 3,841,023 - 3,861,519 - 3,892,982 3,915,384 - 3,951,339 - 3,992,809 4,004,612 - 4,014,135 - 4,035,950 4,051,626 - 4,057,933 - 4,075,785 4,107,875 - 4,332,105